ACPI: blacklist: fix clang warning for unused DMI table

When CONFIG_DMI is disabled, we only have a tentative declaration,
which causes a warning from clang:

drivers/acpi/blacklist.c:20:35: error: tentative array definition assumed to have one element [-Werror]
static const struct dmi_system_id acpi_rev_dmi_table[] __initconst;

As the variable is not actually used here, hide it entirely
in an #ifdef to shut up the warning.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/blacklist.c

@@ -17,7 +17,9 @@
 
 #include "internal.h"
 
+#ifdef CONFIG_DMI
 static const struct dmi_system_id acpi_rev_dmi_table[] __initconst;
+#endif
 
 /*
  * POLICY: If *anything* doesn't work, put it on the blacklist.
@@ -61,7 +63,9 @@ int __init acpi_blacklisted(void)
 	}
 
 	(void)early_acpi_osi_init();
+#ifdef CONFIG_DMI
 	dmi_check_system(acpi_rev_dmi_table);
+#endif
 
 	return blacklisted;
 }